Self-referentially short for PHP: Hypertext
Preprocessor, an open source, server-side, HTML embedded scripting
language used to create dynamic Web pages.
In an HTML document, PHP script (similar syntax to that of Perl or C )
is enclosed within special PHP tags. Because PHP is embedded within
tags, the author can jump between HTML and PHP (similar to ASP and Cold
Fusion) instead of having to rely on heavy amounts of code to output
HTML. And, because PHP is executed on the server, the client cannot view
the PHP code.

PHP can perform any task that any CGI program can do, but its strength
lies in its compatibility with many types of databases. Also, PHP can
talk across networks using IMAP, SNMP, NNTP, POP3, or HTTP.

PHP was created sometime in 1994 by Rasmus Lerdorf. During mid 1997, PHP
development entered the hands of other contributors. Two of them, Zeev
Suraski and Andi Gutmans, rewrote the parser from scratch to create PHP
version 3 (PHP3).